Japanese Patent Application Laid-Open Publication No. 2012-161027 (Patent Document 1) discloses a configuration in which a node redundancy is applied to two edge switching devices disposed at the boundary of a MAC-in-MAC network. In this document, when MAC addresses of one device and the other device are defined as a my representative address and a mate representative address, respectively, each of two edge switching devices controls a stream of frames based on the combination of the my representative address and the mate representative address contained in a destination and a source of a frame. For example, when an encapsulated frame destined for a my representative address is received from a core switch and a destination customer address has not been learned, one of the two edge switching devices decapsulates the encapsulated frame and then relays it to an access port, and further relays the encapsulated frame to the other device via an IC port. Then, the other device also decapsulates the received encapsulated frame and then relays it to an access port.
Japanese Patent Application Laid-Open Publication No. 2012-209984 (Patent Document 2) discloses a configuration in which an inter-device link aggregation is set on each link between a customer edge in a user network and two provider edges in a MPLS network. When the two provider edges receive a packet from the customer edge, only one of the two provider edges relays the packet to the MPLS network based on a rule made in advance between the two provider edges.